findViewById 在片段中不起作用

Question

findViewById 在片段中不起作用 我正在尝试将列表视图添加到特定片段但我无法使用 find viewBy Id 映射列表视图控件我是 android 开发的初学者我不知道实现片段 谁能帮助我？

public class FindPeopleFragment extends Fragment {

public FindPeopleFragment(){}
private static final String TAG = "CardListActivity";
private CardArrayAdapter cardArrayAdapter;
private ListView listView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {


    View rootView = inflater.inflate(R.layout.fragment_find_people, container, false);

    return rootView;

    listView = (ListView) findViewById(R.id.card_listView);

    listView.addHeaderView(new View(this));
    listView.addFooterView(new View(this));

    cardArrayAdapter = new CardArrayAdapter(getApplicationContext(), R.layout.list_item_card);

    for (int i = 0; i < 10; i++) {
        Card card = new Card("Card " + (i+1) + " Line 1", "Card " + (i+1) + " Line 2");
        cardArrayAdapter.add(card);
    }
    listView.setAdapter(cardArrayAdapter);


}
public class CardArrayAdapter  extends ArrayAdapter<Card> {
    private static final String TAG = "CardArrayAdapter";
    private List<Card> cardList = new ArrayList<Card>();

    public class CardViewHolder {
        TextView line1;
        TextView line2;
    }

    public CardArrayAdapter(Context context, int textViewResourceId) {
        super(context, textViewResourceId);
    }

    @Override
    public void add(Card object) {
        cardList.add(object);
        super.add(object);
    }

    @Override
    public int getCount() {
        return this.cardList.size();
    }

    @Override
    public Card getItem(int index) {
        return this.cardList.get(index);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        CardViewHolder viewHolder;
        if (row == null) {
            LayoutInflater inflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.list_item_card, parent, false);
            viewHolder = new CardViewHolder();
            viewHolder.line1 = (TextView) row.findViewById(R.id.line1);
            viewHolder.line2 = (TextView) row.findViewById(R.id.line2);
            row.setTag(viewHolder);
        } else {
            viewHolder = (CardViewHolder)row.getTag();
        }
        Card card = getItem(position);
        viewHolder.line1.setText(card.getLine1());
        viewHolder.line2.setText(card.getLine2());
        return row;
    }

    public Bitmap decodeToBitmap(byte[] decodedByte) {
        return BitmapFactory.decodeByteArray(decodedByte, 0, decodedByte.length);
    }
}

}

Answer 1

您的 oncreateview 应如下所示：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {


    View rootView = inflater.inflate(R.layout.fragment_find_people, container, false);



    listView = (ListView)rootView.findViewById(R.id.card_listView);

    listView.addHeaderView(new View(this));
    listView.addFooterView(new View(this));

    cardArrayAdapter = new CardArrayAdapter(getApplicationContext(), R.layout.list_item_card);

    for (int i = 0; i < 10; i++) {
        Card card = new Card("Card " + (i+1) + " Line 1", "Card " + (i+1) + " Line 2");
        cardArrayAdapter.add(card);
    }
    listView.setAdapter(cardArrayAdapter);

    return rootView;
}

Answer 2

做吧

  listView = (ListView) rootView.findViewById(R.id.card_listView);

并移动

  return rootView;

最后 onCreateView(...)

更正：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {


View rootView = inflater.inflate(R.layout.fragment_find_people, container, false);

listView = (ListView)rootView.findViewById(R.id.card_listView);
listView.addHeaderView(new View(getActivity()));
listView.addFooterView(new View(getActivity()));
............
return rootView;

}

你也应该改变

  listView.addHeaderView(new View(this));
  listView.addFooterView(new View(this));

到

  listView.addHeaderView(new View(getActivity()));
  listView.addFooterView(new View(getActivity()));